Localization of formaldehyde production during frozen storage of European hake (Merluccius merluccius)

The formation of dimethylamine and formaldehyde from trimethylamine N-oxide by the enzyme trimethylamine N-oxide demethylase in whole hake during froz en storage was studied. The objective was to check if there were parts of t he muscle with a higher production of dimethylamine and formaldehyde, and i f the presence of kidney during frozen storage had any significant influenc e on the production. Three variables were examined through one year storage . The first was anatomical location, considering the red muscle and three z ones of white muscle, one located right over the kidneys, the dorsal part o ver the viscera, and the tail. The second variable was the temperature of s torage, -11 degreesC or -18 degreesC. Finally, the influence of kidneys dur ing storage, comparing fish with and without kidneys, was also evaluated. No differences were found in dimethylamine and formaldehyde production betw een fish with and without kidneys stored at -18 degreesC. However at -11 de greesC the amounts of dimethylamine and formaldehyde detected in fish witho ut kidneys were, in some cases, higher than in those with kidneys. Kidney r emoval does not have a statistically significant influence on DMA and FA pr oduction in frozen storage hake. Differences in dimethylamine and formaldeh yde values among different anatomical locations were found, especially in t hose stored over one year. It was found that, in general, the white muscle located right over the kidneys produced more dimethylamine than other parts of the fish.